Interference coordination method, interference coordination device and measurement device

ABSTRACT

A system that determines to modify transmission power of a first small cell: determines an effect of modifying transmission power of the first small cell on a user equipment that is served by the first small cell; and controls modifying the transmission power of the first small cell based on the determination to modify the transmission power and the determined effect of modifying the transmission power on the user equipment that is served by the first small cell.

FIELD OF THE INVENTION

The present invention relates to the field of communication, andparticularly to an interference coordination method, an interferencecoordination device and a measurement device.

BACKGROUND OF THE INVENTION

For an interference problem at the edge of cells, the 3rd GenerationPartnership Project (3GPP) introduces the Inter Cell InterferenceCoordination (ICIC) technology in the R8 version, and introduces theenhanced ICIC (eICIC) in the R10 version, both having multiple resultsand achieving some effect in interference suppression. Furthermore, acore concept of the interference coordination technology in a Long TermEvolution (LTE) system is to employ the frequency reuse technology tomake a distance of interference signal sources between adjacent cells asfar as possible, thus suppressing interference between adjacent cells,and an effect of improving transmission quality and raising throughputis achieved. However, although some effect for suppressing the samefrequency interference between edge users in the cell is achieved by theinterference coordination technology, the frequency of a whole cell islimited by the frequency reuse, which makes the throughput of the wholecell decreased to some extent. Therefore, the interferencecoordination/avoiding technology is equivalent to a compromise betweenthe throughput of the whole system and throughput of the edge users inthe cell, and sacrifices a small part of an entire performance whileimproving the fairness. Furthermore, in a case that small cells aredeployed densely, it is far from enough to solve the interferenceproblem between small cells only depending on the frequency reuse.

SUMMARY OF THE INVENTION

In the following, an overview of the present invention is given simplyto provide basic understanding to some aspects of the present invention.It should be understood that this overview is not an exhaustive overviewof the present invention. It is not intended to determine a criticalpart or an important part of the present invention, nor to limit thescope of the present invention. An object of the overview is only togive some concepts in a simplified manner, which serves as a preorder ofa more detailed description described later.

In view of this, the present invention provides an interferencecoordination method, an interference coordination device and ameasurement device.

According an aspect of the present invention, there is provided a systemthat determines to modify transmission power of a first small cell;determines an effect of modifying the transmission power of the firstsmall cell on a user equipment that is served by the first small cell;and controls modifying the transmission power of the first small cellbased on the determination to modify the transmission power and thedetermined effect of modifying the transmission power on the userequipment that is served by the first small cell.

The system according to an embodiment of the present invention describedabove can lower the interference to the target small cell by, in thecase that the interference to the target small cell satisfies thepredetermined condition, indicating the target small cell base stationto adjust power according to the number of users or indicating thetarget small cell base station to request the other base station orstations to adjust power according to the number of users.

These and other advantages of the present invention will be moreapparent by illustrating in detail a preferred embodiment of the presentinvention in conjunction with accompanying drawings below.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention can be better understood by referring to thedescription hereinafter given in conjunction with the accompanyingdrawings. In all the accompanying drawings, identical or similarcomponents are denoted with identical or similar reference numerals. Theaccompanying drawings together with the detailed description below areincluded in this specification and constitute a part of thisspecification, and are used to further exemplify a preferred embodimentof the present invention and explain principles and advantages of thepresent invention. In the drawings:

FIG. 1A to FIG. 1C show schematic diagrams of deployment scenarios 2a,2b and 3 of small cell in Long Term Evolution-Advanced (LTE-A);

FIG. 2 is a flow chart for schematically showing one exemplaryprocessing of an interference coordination method in a wirelesscommunication system according to an embodiment of the presentinvention;

FIG. 3 is a flow chart for schematically showing one possible exemplaryprocessing of a step S230 as shown in FIG. 2;

FIG. 4 is a flow chart for schematically showing another possibleexemplary processing of a step S230 as shown in FIG. 2;

FIG. 5A to 5D are flow charts for schematically showing four possibleexemplary processing of a further adjustment;

FIG. 6 is a flow chart for schematically showing one possible exemplaryprocessing of a step S240 as shown in FIG. 2;

FIG. 7 is a flow chart for schematically showing other possibleexemplary processing of a step S240 as shown in FIG. 2; and

FIG. 8 is a block diagram for schematically showing one exemplarystructure of an interference coordination device in a wirelesscommunication system according to an embodiment of the presentinvention.

It should be understood by those skilled in the art that elements in theaccompanying drawings are shown only for the purpose of simplicity andclarity, and are not drawn to scale. For example, the sizes of certainelements in the accompanying drawings may be enlarged relative to theother elements, to improve an understanding of the embodiment of thepresent invention.

DETAILED DESCRIPTION OF THE INVENTION

An exemplary embodiment of the present invention will be describedhereinafter in conjunction with the accompanying drawings. For thepurpose of conciseness and clarity, not all features of an embodimentare described in this specification. However, it should be understoodthat multiple decisions specific to the embodiment have to be made in aprocess of developing any such embodiment to realize a particular objectof a developer, for example, conforming to those constraints related toa system and a business, and these constraints may change as theembodiments differs. Furthermore, it should also be understood thatalthough the development work may be very complicated andtime-consuming, for those skilled in the art benefiting from the presentdisclosure, such development work is only a routine task.

Here, it should also be noted that in order to avoid obscuring thepresent invention due to unnecessary details, only a device structureand/or processing steps closely related to the solution according to thepresent invention are illustrated in the accompanying drawing, and otherdetails having little relationship to the present invention are omitted.

An embodiment of the present invention provides an interferencecoordination method in a wireless communication system. The interferencecoordination includes: in a case that interference to a target smallcell satisfies a predetermined condition, the target small cell basestation adjusting power at least based upon the number of users in acoverage area thereof, and/or requesting other small cell base stationor stations producing interference thereto to adjust power at leastbased upon the number of users in a coverage area of the other smallcell base station or stations producing the interference described aboveto lower the interference to the target small cell.

In practical application, the interference coordination method describedabove according to the embodiment of the present invention can beapplied in the small cell deployment scenarios 2a, 2b or 3 in a LTE-AR12 heterogeneous network. FIG. 1A to 1C show schematic diagrams of thesmall cell deployment scenarios 2a, 2b and 3 in LTE-A.

Specifically, in the small cell deployment scenario 2a in LTE-A, a smallcell is in a coverage area of a macro cell, a frequency of the macrocell is different from that of the small cell, and the small cell isoutdoor. As shown in FIG. 1A, BS1, BS2 and BS3 represent three smallcell base stations, a dotted line circle outside of the BS1, BS2 and BS3represents that all the three small cell base stations are in thecoverage area of the macro cell (i.e. in a coverage area of a macro basestation).

In the small cell deployment scenario 2b in LTE-A, a small cell is in acoverage area of a macro cell, a frequency of the macro cell isdifferent from that of the small cell, and the small cell is indoor. Itdiffers from the small cell deployment scenario 2a in LET-A shown inFIG. 1A in that a cuboid outside of the BS1, BS2 and BS3 shown in FIG.1B represents the three small cell base stations are indoor.

Furthermore, in the small cell deployment scenario 3 in LTE-A, there isno macro cell in the wireless communication system, and the small cellis indoor. As shown in FIG. 1C, three small cell base stations BS1, BS2and BS3 are indoors, and there is no macro cell (or macro base station).

It should be noted that in the small cell deployment scenarios 2a and 2bin LET-A, interference between small cells becomes the main interferencesince the frequency of the small cell is different from that of themacro cell; and in the small cell deployment scenario 3 in LET-A, thesmall cell is also only subjected to interference from circumambientsmall cells since there is no macro cell.

In an implementation manner of the interference coordination methodaccording to the embodiment of the present invention, the interferencecoordination method described above can be implemented based uponbaseband cloud (equivalent to a centralized processing). In theimplementation manner, the baseband cloud can receive the interferenceto a first small cell (e.g. a target small cell) and information on thenumber of users, and in a case that the interference to the first smallcell satisfies a predetermined condition, determine corresponding poweradjustment at least based upon the number of users in a coverage areathereof, or determine power adjustment to a second small cell basestation producing interference to the first small cell based upon thenumber of users in a coverage area of the second small cell basestation, and then send an indicator of power adjustment to a first basestation or a second base station.

An exemplary processing of the interference coordination method in thewireless communication system described above is described below inconjunction with FIG. 2.

As shown in FIG. 2, a processing flow 200 of the interferencecoordination method in the wireless communication system according tothe embodiment of the present invention starts from a step S210, andthen performs a step S220.

In the step S220, it is determined whether interference to a targetsmall cell satisfies a predetermined condition. In the case that theinterference to the target small cell satisfies the predeterminedcondition described above, a step S230 and/or a step S240 are performed,and in the case that the interference to the target small celldissatisfies the predetermined condition described above, a step S250 isperformed.

Specifically, the target small cell base station described above may befor example any one of multiple small cell base stations in a coveragearea of the wireless communication system described above.

In an implementation manner of the interference coordination methodaccording to the embodiment of the present invention, the interferenceto the target small cell may be estimated by using transmission power ofrespective small cell base stations in the wireless communicationsystem. In one example, the transmission power of the respective smallcell base stations described above in the wireless communication systemmay be included in an indication signaling exchanged between respectivesmall cell base stations described above. For those skilled in the art,a method for estimating the interference of the respective small cellbase stations described above to the target small cell using an existingalgorithm, according to the transmission power of the respective smallcell base stations described above and a distance between the respectivesmall cell base stations described above and the target small cell basestation can be acquired by referring to common knowledge and/or thedisclosed materials in the art, which is not described in detail hereany more.

Furthermore, in another implementation manner of the interferencecoordination method according the embodiment of the present invention,the interference to the target small cell may also be obtained accordingto interference to users in a coverage area of the target small cellbase station. For example, the interference to the target small cell maycorrespond to interference to all users in the coverage area of thetarget small cell base station, that is, the interference to the targetsmall cell may be equivalent to a sum of the interference to all theusers in the coverage area of the target small cell base station.Specifically, the interference to users in the coverage area of thetarget small cell base station can be obtained for example by ameasurement device arranged at the user, or can also be obtained by thetarget small cell base station itself, for example, in a case that aconfiguration ratio between uplink and downlink of a subframe ofrespective small cell base stations is different in a Time DivisionDuplex (TDD) system, and the like.

In an implementation manner of the interference coordination methodaccording to the embodiment of the present invention, the predeterminedcondition described above may include only a condition as follows: theinterference to the target small cell is above a first predeterminedthreshold (referred to as “a first condition” hereinafter). In thiscase, when the interference to the target small cell satisfies the firstcondition, a step S230 or a step S240 may be performed; if theinterference to the target small cell dissatisfies the first condition,a step S250 may be performed.

In another implementation manner of the interference coordination methodaccording to the embodiment of the present invention, the predeterminedcondition described above may also include only a condition as follows:the target small cell is any one of at least one small cell subjected tothe most serious interference in the wireless communication system or ina predetermined cluster of small cells (referred to as “a secondcondition” hereinafter). In this case, when the interference to thetarget small cell is so serious that the target small cell becomes oneof the at least one small cell subjected to the most seriousinterference in the predetermined cluster of small cells describedabove, a step S230 or a step S240 may then be performed; if the targetsmall cell is not one of the at least one small cell subjected to themost serious interference in the predetermined cluster of small cellsdescribed above, a step S250 may then be performed.

All base stations (such as multiple small cell base stations) in thewireless communication system or in the predetermined cluster of smallcells are ranked according to a degree of interference thereto, forexample, all base stations are ranked according the degree of subjectedinterference, for example from largest to smallest, with “at least onesmall cell subjected to the most serious interference” referring to atleast one small cell ranked in the foremost. Specifically, the numbercorresponding to the “at least one” in the “at least one small cell” maybe preset, for example, may be one, two or more.

For example, provided that the number of all small cells in the wirelesscommunication system or in the predetermined cluster of small cells is5, and the 5 small cells are a first small cell, a second small cell, athird small cell, a fourth small cell and a fifth small cellrespectively. It is assumed that a result of ranking the 5 small cellsaccording to the degree of subjected interference from largest tosmallest is:

the second small cell (subjected interference)>the fourth small cell(subjected interference)>the fifth small cell (subjectedinterference)>the first small cell (subjected interference)>the thirdsmall cell (subjected interference).

Provided that the number corresponding to the “at least one” is presetto 3, the at least one small cell subjected to the most seriousinterference (i.e. 3 small cells subjected to the most seriousinterference) in the wireless communication system or in thepredetermined cluster of small cells described above are the secondsmall cell, the fourth small cell and the fifth small cell.

In another implementation manner of the interference coordination methodaccording to the embodiment of the present invention, the predeterminedcondition described above may include the first condition and the secondcondition described above simultaneously. In this case, if theinterference to target small cell satisfies the first condition and thesecond condition described above simultaneously (i.e. the interferenceto the target small cell is above the first predetermined threshold, andthe target small cell base station is one of the at least one small cellsubjected to the most serious interference in the wireless communicationsystem or in the predetermined cluster of small cells), a step S230 or astep S240 may be performed; or if any one of the first condition and thesecond condition described above is dissatisfied, a step S250 may beperformed.

In practical processing, the first condition and/or the second conditiondescribed above may be chosen as the predetermined condition describedabove according to actual need (can also be chosen according to anempiric value or via an experimental method). Hence, according todifferent communication requirements (or other requirements), the smallcell base stations required to be power adjusted (i.e. the base stationcorresponding to the small cell satisfying the predetermined conditiondescribed above) can be determined in the wireless communication systemor in the predetermined cluster of small cells, and each of thedetermined small cell base stations required to be power adjusted istaken as the target small cell base station described above to performcorresponding processing.

As shown in FIG. 2, in the step S230, the target small cell base stationadjusts power at least based upon the number of users in a coverage areathereof to lower interference to the target small cell. The step S250 isthen performed. For the purpose of convenience, the processing procedureof “the target small cell base station adjusting power at least basedupon the number of users in a coverage area thereof” preformed in thestep S230 is referred to as “a first kind of preliminary adjustment”.

Furthermore, as shown in FIG. 2, in the step S240, the target small cellbase station requests other small cell base station or stations (also bereferred to as “the requested small cell base station” below) producingthe interference thereto to adjust power at least based upon the numberof users in a coverage area of the other small cell base station orstations (i.e. “the requested small cell base station”) producing theinterference described above, to lower the interference to the targetsmall cell. The step S250 is then performed. For the purpose ofconvenience, a processing procedure of “the target small cell basestation requesting other small cell base station or stations producingthe interference thereto to adjust power at least based upon the numberof users in a coverage area of the other small cell base station orstations producing the interference described above” preformed in thestep S240 is referred to as “a second kind of preliminary adjustment”.

In a particular implementation manner (a first particular implementationmanner) of the interference coordination method according to theembodiment of the present invention, the first kind of preliminaryadjustment in step S230 (and/or the second kind of preliminaryadjustment in step S240) may include for example lowering transmissionpower of the small cell base stations (for example, the target smallcell base station in step S230 and/or the requested small cell basestation in step S240) to narrow the coverage area of the small cell basestation, and switching users who leave the coverage area of the smallcell base station while the transmission power of the small cell basestation is lowered to other cell or cells.

Specifically, in one example of the first particular implementationmanner described above, the “other cell or cells” in the “switchingusers who leave the coverage area of the small cell base station whilethe transmission power of the small cell base station is lowered toother cell or cells” may include for example adjacent small cells of thesmall cell base station and a macro cell covering the small cell, andthe adjacent small cells of the small cell base station may have ahigher priority level than that of the macro cell. It should be notedthat “the small cell base station” and “the small cell” described herecorrespond to the same small cell. Hence, in the step S230 (and/or thestep S240), in a case that the adjacent small cells of the small cellbase station and the macro cell all have enough receptivity, edge users(and/or central users) in the coverage area of the small cell basestation are preferably switched to the adjacent small cells thereof.

In an implementation manner of the interference coordination methodaccording to the embodiment of the present invention, for each of allsmall cell base stations included in the wireless communication system(for example, the target small cell base station or any one of smallcell base stations except for the target small cell base station), acoverage area of the small cell base station may include a centralregion and an edge region. Wherein, the central region of the small cellbase station is a region where central users in the coverage area of thesmall cell base station (also referred to as “central users of the smallcell base station” below) are located, and the edge region of the smallcell base station is a region where edge users in the coverage area ofthe small cell base station (also referred to as “edge users of thesmall cell base station” below) are located. Specifically, the centralusers of the small cell base station are users with a signal qualitysatisfying a predetermined quality condition, and the edge users of thesmall cell base station are users with a signal quality dissatisfyingthe predetermined quality condition. It should be illustrated that smallcell base stations except for the target small cell base station mayinclude the requested small cell base station.

In one example, the predetermined quality condition described above maybe a condition set according to a value of Reference Signal Receptionpower (RSRP)/Reference Signal Received Quality (RSRQ). For example, thepredetermined quality condition described above may be that the value ofRSRP/RSRQ is above or equal to a second predetermined threshold. Hence,in this example, the central users of the small cell base stationdescribed above may be users with a value of RSRP/RSRQ being above orequal to the second predetermined threshold described above, and theedge users of the small cell base station described above may be userswith a value of RSRP/RSRQ below the second predetermined threshold.Specifically, for those skilled in the art, the value of RSRP/RSRQ of auser may be obtained from common knowledge and/or in conjunction withthe disclosed materials, which is not described in detail here further.

It should be illustrated that the predetermined quality conditiondescribed above is not limited to the condition set according to thevalue of RSRP/RSRQ described in the above example, and for example canalso be a condition set according to other standards capable ofevaluating signal quality such as a Received Signal Strength Indicator(RSSI), a Signal-to-Interference plus Noise Ratio (SINR), which is notdescribed here further.

Hence, after dividing the users in the coverage area of the small cellbase station into the central users and the edge users, the small cellbase station (such as the target small cell base station or “therequested small cell base station” described above) can adjust power atleast based upon the number of the central users and/or the edge usersthereof.

In another example of the first particular implementation mannerdescribed above, in a case that the coverage area of the small cell basestation (such as the target small cell base station or “the requestedsmall cell base station” described above) includes the central regionand the edge region (i.e., users of the small cell base station includethe central users and the edge users), the processing of the “loweringtransmission power of the small cell base station (such as the targetsmall cell base station in the step S230 and/or the requested small cellbase station in step S240)” can be implemented by for example theprocessing as follows: lowering transmission power of the small cellbase station (such as the target small cell base station in the stepS230 and/or the requested small cell base station in the step S240) at afirst predetermined step size, and switching edge users who leave thecoverage area of the small cell base station while the transmissionpower of the small cell base station is lowered to other cell or cells(such as the adjacent small cells of the small cell base station or themacro cell covering the small cell) until the edge users who leave thecoverage area of the small cell base station cannot be switched to othercell or cells described above.

Furthermore, in one example of the first particular implementationmanner described above, in a case that users who leave the coverage areaof the small cell base station while the transmission power of the smallcell base station (such as the target small cell base station in thestep S230 and/or the requested small cell base station in the step S240)is lowered can be switched to other cell or cells, the transmissionpower of the small cell base station can be at least lowered to be onlycapable of covering the central region thereof.

Furthermore, in another example of the first particular implementationmanner described above, in the case that the coverage area of the smallcell base station (such as the target small cell base station in thestep S230 and/or the requested small cell base station in the step S240)includes the central region and the edge region described above, thetransmission power of the small cell base station can be adjusted to thelowest transmission power thereof. Specifically, the lowest transmissionpower of the small cell base station is a transmission power at whichthe small cell base station cannot transmit a downlink signal to a userthereof, but can communicate with another base station.

In a particular implementation manner (a second particularimplementation manner) of the interference coordination method accordingto the embodiment of the present invention, in a case that the coveragearea of the target small cell base station includes the central regionand the edge region described above, the processing of the step S230 canbe realized for example by steps S310 to S330 shown in FIG. 3.

As shown in FIG. 3, it is determined whether the number of central usersin a coverage area of the target small cell base station (as an exampleof the small cell base station mentioned in the first particularimplementation manner described above) is below a first predeterminednumber in the step S310; if the number of the central users in thecoverage area of the target small cell base station is below the firstpredetermined number, a step S320 or a step S330 is then performed;otherwise, a subsequent processing (for example the step S250) afterstep S230 is performed.

In the step S320, transmission power of the target small cell basestation can be lowered in a corresponding predetermined manner, and theedge users in the coverage area of the target small cell base stationcan be switched to an adjacent small cell or a macro cell having enoughreceptivity to lower interference to users subjected to interference inan original coverage area of the target small cell base station (i.e. acoverage area before the transmission power is lowered). The subsequentprocessing (for example the step S250) after the steps S310 to S330 isthen performed.

In the step S330, transmission power of the target small cell basestation can be lowered in a corresponding predetermined manner, and theedge users and the central users in the coverage area of the targetsmall cell base station can be switched to an adjacent small cell or amacro cell having enough receptivity to lower interference to userssubjected to interference in the coverage area of the target small cellbase station before the transmission power is lowered. The subsequentprocessing (for example the step S250) after the steps S310 to S330 isthen performed. It should be illustrated that the predetermined mannerin the step S330 can be identical to or different from that in the stepS320.

In one example (a first example), in the step S320 and the step S330, itcan be determined whether to switch the edge users (and/or the centralusers) of the target small cell base station to an adjacent small cellthereof or a macro cell, according to the priority level of the adjacentsmall cell of the target small cell base station and the priority levelof the macro cell.

In another example (a second example), in a procedure of performingpower adjustment by the target small cell base station in the step S330,when the central users in the coverage area of the target small cellbase station can be switched to the adjacent small cell thereof (alsoreferred to as “receiving small cell” below), the transmission power ofthe target small cell base station can be adjusted to the lowesttransmission power thereof (as an example of “lowering the transmissionpower of the target small cell base station in a correspondingpredetermined manner”), and the central users and the edge users in theoriginal coverage area of the target small cell base station (i.e., thecoverage area before the transmission power is lowered) are all switchedto the receiving small cell. It should be illustrated that the receivingsmall cell described above may include only one small cell, or mayinclude multiple small cells. In practical processing, the processingdescribed in the second example can be performed for example in a casethat there is no macro cell in the wireless communication system (forexample, when the target small cell base station is located in the smallcell deployment scenario 3 in LET-A).

Furthermore, in still another example (a third example), in a procedureof performing power adjustment by the target small cell base station inthe step S330, if the central users in the coverage area of the targetsmall cell base station cannot be switched to the adjacent small cellsthereof, and cannot be switched to the macro cell either (for example,there is no macro cell in the wireless system), but the edge usersthereof can be switched to the adjacent small cells or the macro cell,the transmission power of the target small cell base station can belowered, so that the lowered transmission power of the target small cellbase station can cover only the central region thereof, and cannot coverthe edge region thereof (as an example of “lowering the transmissionpower of the target small cell base station in a correspondingpredetermined manner”), and the edge users in the original coverage areaof the target small cell base station (i.e., the coverage area beforethe transmission power is lowered) are switched to the adjacent smallcell having enough receptivity. In practical processing, the processingdescribed in the third example can be performed for example in a casethat there is no macro cell in the wireless communication system (forexample, when the target small cell base station is located in the smallcell deployment scenario 3 in LET-A).

Furthermore, in yet another example (a fourth example), in a procedureof performing power adjustment by the target small cell base station inthe step S330, if there is a macro cell in the wireless communicationsystem, and the target small cell base station and the adjacent smallcell base stations thereof are in a coverage area of the macro cell basestation, the transmission power of the target small cell base stationcan be adjusted to the lowest transmission power thereof (as an exampleof “lowering the transmission power of the target small cell basestation in a corresponding predetermined manner”), and the central usersin the original coverage area of the target small cell base station(i.e., the coverage area before the transmission power is lowered) canbe switched to the macro cell described above, and the edge users in theoriginal coverage area of the target small cell base station (i.e., thecoverage area before the transmission power is lowered) can be switchedto the adjacent small cell having enough receptivity. Specifically, inthe fourth example, the target small cell base station may be locatedfor example in the small cell deployment scenario 2a or 2b in LET-A.

In another particular implementation manner (a third particularimplementation manner) of the interference coordination method accordingto the embodiment of the present invention, in a case that the coveragearea of the target small cell base station includes the central regiondescribed above and the edge region described above, the processing inthe step S230 can include for example processing of steps S410 to S420as shown in FIG. 4, and can selectively include processing of the stepsS310 to S330 described in the above second implementation manner inconjunction with FIG. 3. In the following, the particular implementationmanner is described by taking the case that the step S230 includes thesteps S310 to S330 and the steps S410 to S420 as an example, and a casethat the step S230 includes only the steps S410 to S420 can refer to thefollowing description, hence the case is not described any more.

It is determined whether the number of central users in the coveragearea of the target small cell base station is below a firstpredetermined number in step S310: if the number of the central users inthe coverage area of the target small cell base station is below thefirst predetermined number, a step S320 or a step S330 is thenperformed; otherwise, a step S410 is performed. Specifically, processingof step S320, S330 is identical to that in the second particularimplementation manner, and the same effect can be achieved, which is notdescribed here further. However, it should be noted that, in the thirdparticular implementation manner, after the S320 or the S330 isperformed, a subsequent processing (for example the step S250) after thestep S420 is performed.

In one exemplary processing of the step S410 (not shown in FIG. 4), thetransmission power of the target small cell base station can be lowered,so that the lowered transmission power thereof can only cover thecentral region thereof, but cannot cover the edge region thereof, andthe edge users in the original coverage area of the target small cellbase station (i.e., the coverage area before the transmission power islowered) are switched to the adjacent small cells having enoughreceptivity.

Furthermore, in another exemplary processing of the step S410 (as shownin FIG. 4), it is determined whether a ratio of the number of thecentral users to the number of the edge users in the coverage area ofthe target small cell base station is above or equal to a thirdpredetermined threshold: if the ratio is above or equal to the thirdpredetermined threshold, a step S420 is then performed; otherwise, asubsequent processing (for example the step S250) after the step S420 isthen performed.

In the step S420 (as shown in FIG. 4), the transmission power of thetarget small cell base station is lowered, so that the loweredtransmission power can only cover the central region thereof, but cannotcover the edge region thereof, and the edge users in the originalcoverage area of the target small cell base station (i.e., the coveragearea before the transmission power is lowered) are switched to theadjacent small cells having enough receptivity.

Furthermore, in one implementation manner of the interferencecoordination method according to the embodiment of the presentinvention, the step S230 can include the following processing: thetarget small cell base station can adjust power based upon interferenceto users in the coverage area thereof.

A processing procedure of “the target small cell base station adjustingpower based upon interference to users in the coverage area thereof”performed in step S230 is referred to as “a further adjustment” below.It should be illustrated that in some implementation manners accordingthe embodiment of the present invention, the step S230 can alsoselectively include the first kind of preliminary adjustment describedabove besides including the further adjustment described above (forexample, the further adjustment described above can be performed afterthe first kind of preliminary adjustment), which is not described herefurther.

In one example (a fifth example), the further adjustment described abovecan be implemented by steps S510 to S530 as shown in FIG. 5A.

As shown in FIG. 5A, in a step S510, at least one user subjected to themost serious interference can be selected from all users subjected tointerference in the coverage area of the target small cell base station.A step S520 is then performed.

In the step S520, for each (indicated by U_(a) below) of the at leastone user subjected to the most serious interference selected in the stepS510, it is determined whether a first adjacent small cell base stationcorresponding to the highest reception power among reception power ofthe user U_(a) from at least one adjacent small cell base station of thetarget small cell base station can accept the user (for example, whetherthe remaining resources is enough to accept this user); if the firstadjacent small cell base station can accept the user, a step S530 isthen performed; otherwise, a subsequent processing (for example the stepS250) after the further adjustment is performed.

In the step S530, the user U_(a) is switched to the first adjacent smallcell base station described above. A subsequent processing (for example,the step S250) after the further adjustment is then performed.

In another example (a sixth example), the further adjustment describedabove can also include steps S510 to S550 as shown in FIG. 5B.

Specifically, processing of the steps S510, S520 and S530 shown in FIG.5B may be identical to those of the steps S510, S520 and S530 describedabove in conjunction with FIG. 5A respectively, and can achieve the sameeffect, thus the processing of the steps S510, S520 and S530 shown inFIG. 5B are not described in detail here further.

It should be illustrated that in the step S520 shown in FIG. 5B, if itis determined that the first adjacent small cell base station cannotaccept this user, a step S540 is then performed.

In the step S540, it is determined whether the target small cell basestation is located in a coverage area of a macro cell: if the targetsmall cell base station is located in the coverage area of the macrocell, a step S550 is then performed; otherwise, a subsequent processing(for example the step S250) after the further adjustment is performed.

In the step S550, the user U_(a) is switched to the macro cell describedabove. Specifically, the macro cell can accept the user. Then, asubsequent processing (for example the step S250) after the furtheradjustment is performed.

Specifically, in the sixth example, the target small cell base stationcan be located for example in the small cell deployment scenario 2a or2b in LTE-A.

In another example (a seventh example), the further adjustment describedabove can also include steps S510 to S560 as shown in the FIG. 5C.

Specifically, processing of the steps S510 to S550 shown in FIG. 5C maybe identical to those of the steps S510 to S550 described above inconjunction with FIG. 5B respectively, and can achieve the same effect,thus the processing of the steps S510 to S550 shown in FIG. 5C are notdescribed in detail here further.

It should be illustrated that if it is determined that the target smallcell base station is not located in the coverage area of the macro cellin the step S540 shown in FIG. 5C, a step S560 is then performed.

In the step S560, a second adjacent small cell base stationcorresponding to the highest reception power of the user is selectedfrom one or more adjacent small cell base stations capable of acceptingthe user among the at least one adjacent small cell base station of thetarget small cell base station except the first adjacent small cell basestation, to switch the user U_(a) to the small cell where the secondadjacent small cell base station is located. Then, a subsequentprocessing (for example the step S250) after the further adjustment isperformed.

It should be illustrated that in other examples, the further adjustmentdescribed above may also include only the steps S510 to S540 and S560shown in FIG. 5C, but may not include the step S550. In this case, if itis determined that the target small cell base station is located in thecoverage area of the macro cell in the step S540, a subsequentprocessing (for example the step S250) after the further adjustment canbe performed. Other processing in this case may be identical to theother processing in the seventh example, and will not be described herefurther.

In addition, in another example (an eighth example), the furtheradjustment described above may also include steps S510 to S570 as shownin FIG. 5D.

Specifically, processing of the steps S510 to S560 shown in FIG. 5D canbe identical to the processing of the steps S510 to S560 described abovein conjunction with FIG. 5C respectively, and can achieve the sameeffect, thus the processing of the steps S510 to S560 shown in FIG. 5Dare not described in detail here further.

It should be illustrated that if a second adjacent small cell basestation conforming to the condition is not found in the step S560 shownin FIG. 5D, a step S570 is then performed.

In the step S570, the transmission power of the target small cell basestation is raised so that the user U_(a) can operate normally. Then, asubsequent processing (for example the step S250) after the furtheradjustment is performed.

Specifically, in the seventh example or the eighth example describedabove, the target small cell base station can be located for example inthe small cell deployment scenario 3 in LTE-A.

Hence, each of the at least one user subjected to the most seriousinterference described above can be switched to other small cell ormacro cell by employing the processing above described in conjunctionwith any one of the FIGS. 5A to 5C, therefore, the at least one usersubjected to the most serious interference can be switched to acorresponding other small cell or a macro cell respectively.

In still another example (a ninth example), after the at least one usersubjected to the most serious interference are all switched to thecorresponding other small cell or the macro cell, the transmission powerof the target small cell base station can be lowered in a correspondingpredetermined manner.

In one example, the step of “the transmission power of the target smallcell base station is lowered in a corresponding predetermined manner”can be realized by the following processing: according to a differencebetween the highest reception power and the lowest reception power ofthe at least one user subjected to the most serious interferencedescribed above for the target small cell base station, and according toa difference between the highest reception power of the at least oneuser subjected to the most serious interference described above for thetarget small cell base station and the lowest reception power of theother user or users except the at least one user subjected to the mostserious interference of the target small cell base station for thetarget small cell base station, determining lowered transmission powerof the target small cell base station; and according the determinedlowered transmission power of the target small cell base stationdescribed above, lowering the transmission power of the target smallcell base station.

For example, it is assumed that original transmission power of thetarget small cell base station is P_(tp-0), the number of the at leastone user subjected to the most serious interference is m, provided thata user with the highest reception power for the target small cell basestation among the m users subjected to the most serious interference isthe i-th user, the reception power of the i-th user for the target smallcell base station is denoted by P_(rp-i), and provided that a user withthe lowest reception power for the target small cell base station amongthe m users subjected to the most serious interference is a j-th user,the reception power of the j-th user for the target small cell basestation is denoted by P_(rp-j). In addition, provided that a user withthe lowest reception power for the target small cell base station amongother users except the m users subjected to the most seriousinterference of the target small cell base station is a k-th user, thereception power of the k-th user for the target small cell base stationis denoted by P_(rp-k). Therefore, the adjusted transmission power ofthe target small cell base station can be calculated from an equation asfollows:P _(tp) =P _(tp-0)−(P _(rp-i) −P _(rp-j))−α(P _(rp-k) −P _(rp-i))

where P_(tp) is the adjusted transmission power of the target small cellbase station, and α is an adjustment factor, which can be determinedaccording a particular implementation situation (or may also accordingto an empirical value or via an experimental method).

In another example, the step of “the transmission power of the targetsmall cell base station is lowered in a corresponding predeterminedmanner” described above can be realized by the following processing:gradually lowering the transmission power of the target small cell basestation at a second predetermined step size, until all of the at leastone user subjected to the most serious interference are not located inthe coverage area of the target small cell base station; and switchingusers who leave the coverage area of the target small cell base stationwhile the transmission power of the target small cell base station islowered to an adjacent small cell or a macro cell.

Furthermore, after the further processing described in any one of thefifth example to the ninth example above is finished, optionally, in acase that a user in a Radio Resource Control (RRC) idle state requestsfor a connection after leaving an original service small cell thereof,cell reselection can be conducted for the user in the RRC idle state tohave the user access to another small cell or a macro cell with enoughreceptivity.

In a particular implementation manner (a fourth implementation manner),when other small cell base station receives a request to adjust power(the request may come from for example the target small cell basestation or may also come from the baseband cloud), if the number of edgeusers in the coverage area of the other small cell base station is belowa second predetermined number, then transmission power of the othersmall cell base station can be lowered, and if the number of edge usersin the coverage area of the other small cell base station is above orequal to the second predetermined number, then the other small cell basestation described above can reject the request.

In one example of the particular fourth implementation, in a case thatthe request described above comes from the target small cell basestation, and the other small cell base station described above rejectsthe request, the transmission power of the target small cell basestation can be raised to have the users in the coverage area of thetarget small cell base station, subjected to the interference of theother small cell base station described above operate normally.

An exemplary processing of the second kind of preliminary adjustmentperformed in the step S240 will be described below in conjunction withthe FIG. 6. In the exemplary processing, in a case that a coverage areaof the requested small cell base station includes a central region andan edge region, when the requested small cell base station receives arequest to adjust power for example from the target small cell basestation or the baseband cloud, the second kind of preliminary adjustmentperformed in the step S240 can be realized by steps S610 to S620 shownin FIG. 6.

As shown in FIG. 6, when the requested small cell base station receivesa request to adjust power from the target small cell base station, astep S610 is performed.

In the step S610, it is determined whether the number of edge users inthe coverage area of the requested small cell base station is below asecond predetermined number: if the number of edge users in the coveragearea of the requested small cell base station is below the secondpredetermined number, a step S620 is performed; otherwise, a subsequentprocessing (for example the step S250) after the step S620 is performed.

In the step S620, the transmission power of the requested small cellbase station is lowered, and edge users who leave the coverage area ofthe requested small cell base station while the transmission power ofthe requested small cell base station is lowered can be switched to anadjacent small cell of the requested small cell base station or a macrocell having enough receptivity.

In one example (a tenth example), processing of the step S620 can berealized by the following processing: lowering transmission power of therequested small cell base station at a first predetermined step size,and switching edge users who leave the coverage area of the requestedsmall cell base station while the transmission power of the requestedsmall cell base station is lowered to an adjacent small cell of therequested small cell base station or a macro cell, until the adjacentsmall cell of the requested small cell base station or the macro celldoes not have enough resources to accept the edge users described abovewho leave the coverage area of the requested small cell base station.

In another example (an eleventh example), the step S240 may also includesteps S710 to S730 shown in FIG. 7.

In step S710, it is determined whether the number of the edge users inthe coverage area of the requested small cell base station is below thesecond predetermined number; if the number of the edge users in thecoverage area of the requested small cell base station is below thesecond predetermined number, a step S720 is then performed; otherwise, astep S730 is performed.

Specifically, processing of the steps S710 and S720 are identical to theprocessing of the steps S610 and S620 described above in conjunctionwith FIG. 6 respectively, and the same effect can be achieved, thusprocessing of the steps S710 and S720 are not described in detail herefurther. It should be illustrated that after the step S720 is performed,a subsequent processing (for example the step S250) after the step S730is performed.

In a step S730, the requested small cell base station rejects therequest of the target small cell base station described above. Then, asubsequent processing (for example the step S250) after the step S730 isperformed.

Furthermore, in another example (a twelfth example), the step S240 canalso selectively include a step S740 as shown in FIG. 7 besidesincluding the steps S710 to S730 as shown in FIG. 7. Specifically, thestep S740 is performed after the step S730.

In the step S740, the requested small cell base station has rejected therequest of the target small cell base station described above, in thiscase, the transmission power of the target small cell base station canbe raised to have users in the coverage area of the target small cellbase station, subjected to the interference of the other small cell basestation operate normally. After the step S740 is performed, a subsequentprocessing (for example the step S250) can be performed, for example.

In addition, in yet another example (a thirteenth example), the stepS240 can also selectively include a step S750 as shown in FIG. 7 besidesincluding the steps S710 to S740 as shown in FIG. 7. Specifically, thestep S750 is performed after the step S730.

In the step S750, the requested small cell base station can reply to thetarget small cell base station, to notify the target small cell basestation of a result that the requested small cell base station acceptsor rejects the request from the target small cell base station. Afterthe step S750 is performed, a subsequent processing (for example thestep S250) can be performed, for example.

In one implementation manner of the interference coordination methodaccording to the embodiment of the present invention, after theprocessing of the step S230 or the step S240 described above, iftransmission power of the small cell base station (for example, thetarget small cell base station or any one small cell base station exceptthe target small cell base station) is the lowest transmission powerthereof or covers only the central region thereof, in a case that thenumber of users initiating service requests in the original coveragearea of the small cell base station for a past first predetermined timeperiod exceeds a third predetermined number, or in a case that othersmall cell cannot satisfy service requests of extra users, the smallcell base station can raise transmission power thereof at a thirdpredetermined step size, until all the users initiating the servicerequests are accessed to the small cell base station, or until a newuser can not access over remaining resources of the small cell basestation. Specifically, the first predetermined time period is forexample a certain time range of day, such as 9:00 a.m to 10:00 a.m ofday, 3:00 p.m to 5:00 p.m of day, or the like.

In one example, if the transmission power of the target small cell basestation (as an example of the small cell base station described above)is the lowest transmission power thereof or covers only the centralregion thereof, and it is known from the historical statisticalinformation that the number of users initiating service requests in thecoverage area of the target small cell base station within a time periodfrom 9:00 a.m to 10:00 a.m of day is above the third predeterminednumber (for example 50), the target small cell base station can raisethe transmission power thereof at the third predetermined step size,until all the users initiating the service requests are accessed to thetarget small cell base station.

In another example, if the transmission power of the target small cellbase station (as an example of the small cell base station describedabove) is the lowest transmission power thereof or covers only thecentral region thereof, when an adjacent small cell of the target smallcell base station cannot satisfy service requests of extra users andthus sends a request to accept the extra users to the target small cellbase station, the target small cell base station can raise thetransmission power thereof at the third predetermined step size to havethe target small cell base station accept the extra users describedabove, until a new user can not access over remaining resources of thetarget small cell base station.

In addition, in one implementation manner of the interferencecoordination method according to the embodiment of the presentinvention, after the step S240 described above is performed, in a casethat the requested small cell base station described above accepts therequest from the target small cell base station, and thus adjusts power,if the requested small cell base station does not receive a request toadjust power from any other small cell base station (including thetarget small cell base station) within a second predetermined timeperiod thereafter, the requested small cell base station can raisetransmission power thereof, for example, at a fifth predetermined stepsize.

Furthermore, in one implementation manner of the interferencecoordination method according to the embodiment of the presentinvention, for any one small cell base station in the target small cellbase station described above and other respective small cell basestations included in the wireless communication system, if the number ofusers of the small cell base station is below a fourth predeterminednumber, then transmission power of the small cell base station islowered at a fourth predetermined step size so that the loweredtransmission power of the small cell base station can ensure theconnection of users thereof.

In another implementation manner of the interference coordination methodaccording to the embodiment of the present invention, in a LTE-TDDsystem (as an example of the wireless communication system), when thetarget small cell subjects to interference from one or more small cellbase stations in other clusters of small cells, the target small cellbase station can transmit requests to adjust power to the one or moresmall cell base stations in the other clusters of small cells describedabove producing the interference to the target small cell, that is,requests the one or more small cell base stations in the other clustersof small cells described above to adjust power to lower the interferenceto the target small cell. Specifically, the requests to adjust powertransmitted to the one or more small cell base stations in the otherclusters of small cells described above can include for example a nameor an identity (ID) of the small cell base station to be power adjustedand an indicator of power adjustment thereof to be performed. Wherein,the indicator of power adjustment can for example include at least oneof lowering power and lowering interference timeslots. Hence, the one ormore small cell base stations in the other clusters of small cells canadjust the transmission power thereof according to the request of poweradjustment described above transmitted from the target small cell basestation.

In one example, in the LTE-TDD system (as an example of the wirelesscommunication system) described above, for each cluster of small cellsin the other clusters of small cells, interference of one or more smallcell base stations in another cluster of small cells (for example, anyone cluster of small cells in the other clusters of small cellsdescribed above) to the target small cell can be interference from alltimeslots of the multiple small cell base stations in the anothercluster of small cells described above, can be interference from acertain timeslot of the multiple small cell base stations in the clusterof small cells described above, and can also be interference from alltimeslots of one small cell base station in the another cluster of smallcells described above, or can be interference from one timeslot of onesmall cell base station in the another cluster of small cells describedabove.

In another example, in the LTE-TDD system (as an example of the wirelesscommunication system) described above, in a case that the target smallcell base station subjects to interference from one or more small cellbase stations in other clusters of small cells, the one or more smallcell base stations in the other clusters of small cells described aboveproducing the interference to the target small cell base station canlower power thereof on the timeslots where the interference to thetarget small cell base station is produced (for example, lower to apreset power value, in which, the preset power value can be determinedfrom an empirical value or via an experimental method), to lower theinterference to the target small cell base station produced by itself.

In one implementation manner of the interference coordination methodaccording to the embodiment of the present invention, in a case that thetarget small cell base station is located in a coverage area of a macrocell in the wireless communication system (for example, the target smallcell base station is located in the small cell deployment scenario 2a or2b in LTE-A), if the ping-pang handover between at least two of thetarget small cell base station and other respective small cell basestations occurs to a user, the user occurring the ping-pang handover canbe switched to the macro cell.

It should be illustrated that the first predetermined threshold to thethird predetermined threshold, the first predetermined number to thefourth predetermined number, the first predetermined step size to thefifth predetermined step size and the first predetermined time periodand the second predetermined time period described above are acquiredfrom empirical values respectively, or can be determined by experimentalmethods, which are not described here anymore.

In addition, it should be illustrated that in one implementation mannerof the interference coordination method according to the embodiment ofthe present invention, if interference to the target small cellsatisfies the predetermined condition, any one of the step S230 and thestep S240 can be performed, or one of the step S230 and the step S240can be performed first, and when a processing result obtained from thestep performed first cannot make the interference to the target smallcell lower to a predetermined degree, the other step of the step S230and the step S240 can then be performed. Furthermore, in otherimplementation manners, when the interference to the target small cellsatisfies the predetermined condition, the step S230 and the step S240can also be performed simultaneously, for example, a power amplitude ofthe target small cell base station to be adjusted in the step S230 and apower amplitude of the requested small cell base station to be adjustedin the step S240 can be allocated according to a certain proportion.

The processing flow 200 ends at the step S250.

It can be known from the above description that the interferencecoordination method described above according to the embodiment of thepresent invention can lower the interference to the target small cellby, in a case that the interference to the target small cell basestation satisfies a predetermined condition, indicating the target smallcell base station to adjust power according the number of users, orindicating the target small cell base station to request other basestation or stations to adjust power according to the number of users.Furthermore, the interference coordination method according to theembodiment of the present invention described above can save energy bypower adjustment. In addition, in some embodiments, the interferencecoordination method according to the embodiment of the present inventionadjusts a coverage area of the small cell by dynamically controllingdownlink power to significantly lower interference between cells.Therefore, network performance can be enhanced well while ensuring userservice quality.

The embodiment of the present invention also provides an interferencecoordination device in the wireless communication system, theinterference coordination device includes: a determination unitconfigured to determine whether interference to a target small cellsatisfies a predetermined condition; and a control unit configured to,in a case that the interference to the target small cell satisfies thepredetermined condition, to control the target small cell base stationto adjust power at least based upon the number of users in a coveragearea thereof, and/or to control the target small cell base station torequest other small cell base station or stations producing theinterference thereto to adjust power at least based upon the number ofusers in a coverage area of the other small cell base station orstations producing the interference described above to lower theinterference to the target small cell.

In one implementation manner of the interference coordination device inthe wireless communication system according to the embodiment of thepresent invention, each base station (for example, each of small cellbase stations and macro base stations) can be provided with acorresponding interference coordination device. Furthermore, in anotherimplementation manner, the interference coordination device describedabove can also be provided at the baseband cloud, so that each basestation (for example, each of small cell base stations and macro basestations) can determine whether the subjected interference theretosatisfies the predetermined condition, if the subjected interferencethereto satisfies the predetermined condition, the base station reportsinformation such as the interference and the number of users (ordirectly communicates all interference situation, and the baseband cloudthen determine whether the interference satisfies the predeterminedcondition) to the interference coordination device, then the basebandcloud determines power adjustment (for example, indicating a basestation subjected to the interference to adjust power itself orindicating a base station serving as the interference source to adjustpower correspondingly).

Furthermore, in one implementation manner of the interferencecoordination device in the wireless communication system according tothe embodiment of the present invention, the interference coordinationdevice can be provided for example at a small cell base station side ora macro base station side.

FIG. 8 is an exemplary structure for schematically illustrating aninterference coordination device in the wireless communication systemaccording to the embodiment of the present invention. As shown in FIG.8, the interference coordination device 800 includes a determinationunit 810 and a control unit 820.

The determination unit 810 is configured to determine whetherinterference to a target small cell satisfies a predetermined condition.Specifically, the processing performed by the determination unit 810 canbe similar to for example the processing of the step S220 in theinterference coordination method described above in conjunction withFIG. 2 to FIG. 7, and can achieve the same effect, thus the processingperformed by the determination unit 810 is not described here further.

Furthermore, the control unit 820 is configured, in a case that theinterference to the target small cell satisfies the predeterminedcondition, to perform the processing of the step S230 in theinterference coordination method described above in conjunction withFIG. 2 to FIG. 7, or to perform the processing of the step S240 in theinterference coordination method described above in conjunction withFIG. 2 to FIG. 7, and can achieve the same effect, which are notdescribed here further.

It can be known from the above description that the interferencecoordination device according to the embodiment of the present inventioncan lower the interference to the target small cell base station by, inthe case that the interference to the target small cell satisfies thepredetermined condition, indicating the target small cell base stationto adjust power according to the number of users, or indicating thetarget small cell base station to request other base station or stationsto adjust power according the number of users. Furthermore, theinterference coordination device according to the embodiment of thepresent invention described above can save energy by power adjustment.In addition, in some embodiments, the interference coordination deviceaccording to the embodiment of the present invention described aboveadjusts the coverage area of the small cell by dynamically controllingdownlink power to significantly lower the interference between cells.Therefore, network performance can be enhanced well while ensuring userservice quality.

It should be illustrated that component units in the interferencecoordination device in the wireless communication system according tothe embodiment of the present invention described above can performprocessing similar to the processing of a corresponding step or acorresponding sub-step in the interference coordination method in thewireless communication system above described in conjunction with theFIG. 2 to FIG. 7, achieving the similar function or effect, which is notdescribed here further.

Furthermore, it should also be illustrated that the interferencecoordination method, the interference coordination device and themeasurement device according the embodiment of the present invention canbe applied to the small cell deployment scenarios 2a, 2b and 3 in LET-Adescribed above, but an application scenario of the interferencecoordination method, the interference coordination device and themeasurement device described above is not limited thereto, and theinterference coordination method, the interference coordination deviceand the measurement device described above can be applied to othersimilar scenario by those skilled in the art in conjunction with theabove description.

Furthermore, the embodiment of the present invention also provides ameasurement device in the wireless communication system, the measurementdevice includes: a measurement unit configured to obtain interference toeach user in a coverage area of each small cell base station in thewireless communication system and to transmit the interference to eachuser to a service base station of the user, in which, the service basestation of the user is provided with the interference coordinationdevice described above.

In the above description for each embodiment of the present invention,features described and/or shown for one embodiment (implementationmanner, example and so on) can be used in one or more other embodiments,combined with features in other embodiments, or substitute features inthe other embodiments, in the same or similar manner.

Furthermore, the method in each embodiment of the present invention isnot limited to be performed according to a time sequence described inthe specification or shown in the accompanying drawings, and can beperformed in parallel or separately or according to other timesequences. Therefore, the sequence for performing the method describedin this specification does not limit the technical scope of the presentinvention.

The embodiments disclosed in the specification may also be configuredaccording to the embodiments outlined below.

According to an exemplary embodiment there is provided a systemincluding circuitry configured to determine to modify transmission powerof a first small cell; determine an effect of modifying the transmissionpower of the first small cell on a user equipment that is served by thefirst small cell; and control modifying the transmission power of thefirst small cell based on the determination to modify the transmissionpower and the determined effect of modifying the transmission power onthe user equipment that is served by the first small cell.

According to the above system, the first small cell is provided in asame area as a macro cell, the first small cell having a smallercoverage area than the macro cell.

According to the above system, the circuitry is configured to determineto modify transmission power of the first small cell when it isdetermined that interference in the first small cell or a second smallcell located adjacent to the first small cell exceeds a predeterminedthreshold value.

According to the above system, the circuitry is configured to controlthe first small cell to reduce transmission power when it is determinedthat the interference in the first small cell or a second small celllocated adjacent to the first small cell exceeds a predeterminedthreshold value.

According to the above system, the circuitry is configured to controlincreasing the transmission power when a predetermined condition issatisfied, the predetermined condition including at least one of theinterference in the first small cell or a second small cell locatedadjacent to the first small cell reducing below the predeterminedthreshold value; a number of user equipment requesting access to thefirst small cell exceeds a predetermined threshold value; and storedscheduling information indicates that the transmission power of thefirst small cell should be increased at a predetermined time and/ordate.

According to the above system, a coverage area of the first small cellincludes a central region including user equipment having a first levelof interference and an edge region including user equipment having asecond level of interference that is greater than the first level ofinterference.

According to the above system, the circuitry is configured to determinethe effect of modifying the transmission power of the first small cellbased on a number of user equipment in the central region and a numberof user equipment in the edge region.

According to the above system, the circuitry is configured to not reducethe transmission power of the first small cell when the number of userequipment in the edge region exceeds a predetermined threshold value.

According to the above system, the circuitry is configured to reduce thetransmission power of the first small cell until it is determined thatuser equipment no longer capable of accessing the first small cell arenot able to be handed over to another cell.

According to the above system, the circuitry is configured to determinewhether the number of user equipment in the central region of thecoverage area of the first small cell is less than a predeterminedthreshold value.

According to the above system, the circuitry is configured to reducetransmission power of the first small cell to service only userequipment located in the central region of the cell when the number ofuser equipment in the central region of the coverage area of the firstsmall cell is greater than the predetermined threshold value.

According to the above system, the circuitry is configured to reducetransmission power of the first small cell such that the first smallcell is not able to transmit a downlink signal to a user equipment, butis capable of communicating with another base station when the number ofuser equipment in the central region of the coverage area of the firstsmall cell is less than the predetermined threshold value.

According to the above system, the circuitry is configured to determinea ratio of the number of user equipment in the central region and thenumber of user equipment in the edge region.

According to the above system, the circuitry is configured to reducetransmission power of the first small cell to service only userequipment located in the central region of the cell when the ratio ofthe number of user equipment in the central region of the coverage areaof the first small cell is greater than a predetermined threshold value.

According to the above system, the circuitry is configured to identify afirst user equipment served by the first small cell that is subject to ahighest level of interference among a plurality of user equipment servedby the first small cell.

According to the above system, the circuitry is configured to determinewhether the first user equipment is capable of being handed over to amacro cell serving the same area of the first small cell or second smallcell adjacent to the first small cell.

According to the above system, the circuitry is configured to instructthe first user equipment to handover to the macro cell or the secondsmall cell and control reduction of the transmission power of the firstsmall cell based on the handover of the first user equipment.

According to the above system, the circuitry is configured to: determinethat reducing the transmission power of the first small cell would causea user equipment that is not capable of being handed over to anothercell to no longer be capable of accessing the first small cell or causea number of user equipment above a threshold value to no longer becapable of accessing the first small cell; and control reducingtransmission power of a second small cell causing interference to thefirst small cell or control increasing transmission power of the firstsmall cell when it is determined that reducing the transmission power ofthe first small cell would cause the user equipment that is not capableof being handed over to another cell to no longer be capable ofaccessing the first small cell or cause a number of user equipment abovea threshold value to no longer be capable of accessing the first smallcell.

According to another exemplary embodiment there is provided anon-transitory computer-readable medium including computer-readableinstructions, which when executed by a system, cause the system to:determine to modify transmission power of a first small cell; determinean effect of modifying the transmission power of the first small cell ona user equipment that is served by the first small cell; and controlmodifying the transmission power of the first small cell based on thedetermination to modify the transmission power and the determined effectof modifying the transmission power on the user equipment that is servedby the first small cell.

According to another exemplary embodiment there is provided a methodperformed by a system, the method comprising: determining, by circuitryof the system, to modify transmission power of a first small cell;determining, by circuitry of the system, an effect of modifying thetransmission power of the first small cell on a user equipment that isserved by the first small cell; and controlling, by circuitry of thesystem, modifying the transmission power of the first small cell basedon the determination to modify the transmission power and the determinedeffect of modifying the transmission power on the user equipment that isserved by the first small cell.

According to another exemplary embodiment there is provided aninterference coordination method in a wireless communication system,comprising: in a case that interference to a target small cell satisfiesa predetermined condition, the target small cell base station adjustingpower at least based upon the number of users in a coverage areathereof, and/or requesting other small cell base station or stationsproducing interference thereto to adjust power at least based upon thenumber of users in a coverage area of the other small cell base stationor stations producing the interference to lower the interference to thetarget small cell.

According to the above method, the predetermined condition comprises:that the interference to the target small cell is above a firstpredetermined threshold; and/or that the target small cell is any of atleast one small cell subjected to the most serious interference in thewireless communication system or in a predetermined cluster of smallcells.

According to the above method, the interference to the target small cellis estimated according to transmission power of respective small cellbase stations in the wireless communication system; or the interferenceto the target small cell corresponds to interference to the users in thecoverage area of the target small cell base station.

According to the above method, a small cell base station adjusting powercomprises lowering transmission power of the small cell base station tonarrow the coverage area of the small cell base station, and switchingusers who leave the coverage area of the small cell base station whilethe transmission power of the small cell base station is lowered toother cell or cells.

According to the above method, for each small cell base station of thetarget small cell base station and other respective small cell basestations comprised in the wireless communication system, a coverage areaof the small cell base station comprises a central region and an edgeregion, wherein the central region is a region where central users witha signal quality satisfying a predetermined quality condition arelocated, and the edge region is a region where edge users with a signalquality dissatisfying the predetermined quality condition are located;and the respective small cell base stations adjust power at least basedupon the number of the central users and/or the edge users thereof.

According to the above method, the predetermined quality conditioncorresponds to that an RSRP/RSRQ value is above or equal to a secondpredetermined threshold.

According to the above method, the other cell or cells comprise anadjacent small cell of the small cell base station and a macro cellcovering the small cell, and wherein the adjacent small cell has ahigher priority level than that of the macro cell.

According to the above method, the lowering transmission power of thesmall cell base station comprises: lowering the transmission power ofthe small cell base station at a first predetermined step size, andswitching edge users who leave the coverage area of the small cell basestation while the transmission power of the small cell base station islowered to other cell or cells until the edge users who leave thecoverage area of the small cell base station cannot be switched to theother cell or cells.

According to the above method, in a case that the users who leave thecoverage area of the small cell base station while the transmissionpower of the small cell base station is lowered can be switched to theother cell or cells, transmission power of the small cell base stationis at least lowered to be only capable of covering the central regionthereof.

According to the above method, in a case that the number of centralusers in the coverage area of the small cell base station is below afirst predetermined number, transmission power of the small cell basestation is adjusted to the lowest transmission power thereof, andwherein the lowest transmission power of the small cell base station istransmission power at which the small cell base station cannot transmita downlink signal to a user thereof but can communication with anotherbase station.

According to the above method, when other small cell base stationreceives a request to adjust power, if the number of edge users in thecoverage area of the other small cell base station is below a secondpredetermined number, then transmission power of the other small cellbase station is lowered, and if the number of edge users in the coveragearea of the other small cell base station is above or equal to thesecond predetermined number, then the other small cell base stationrejects the request.

According to the above method, in a case that the other small cell basestation rejects the request, transmission power of the target small cellbase station is raised to have users, in the coverage area of the targetsmall cell base station, subjected to the interference of the othersmall cell base station operate normally.

According to the above method, for each of at least one user subjectedto the most serious interference in the coverage area of the targetsmall cell base station, in a case that a first adjacent small cell basestation corresponding to the highest reception power among receptionpower of the users for at least one adjacent small cell base station ofthe target small cell base station can accept the user, switching theuser to the first adjacent small cell base station, and in a case thatthe first adjacent small cell base station cannot accept the user, ifthe target small cell base station is in a coverage area of a macrocell, then switching the user to the macro cell.

According to the above method, in a case that a user in a RRC idle staterequests for a connection after leaving an original service small cellthereof, cell reselection is conducted for the user in the RRC idlestate to have the user access to another small cell or a macro cell.

According to the above method, in a case that transmission power of asmall cell base station is the lowest transmission power thereof orcovers only the central region thereof, when the number of usersinitiating service requests in the original coverage area of the smallcell base station for a past first predetermined time period exceeds athird predetermined number, or when other cell cannot satisfy servicerequests of extra users, the small cell base station raisingtransmission power thereof at a third predetermined step size until allthe users initiating the service requests are accessed, or until a newuser cannot access over remaining resources of the small cell basestation.

According to the above method, for any of the target small cell basestation and other respective small cell base stations comprised in thewireless communication system, if the number of users of the small cellbase station is below a fourth predetermined number, then loweringtransmission power of the small cell base station at a fourthpredetermined step size so that lowered transmission power of the smallcell base station can ensure a connection of users thereof.

According to the above method, the request to adjust power comprises: aname or an ID of the small cell base station to be power adjusted and anindicator of power adjustment thereof to be performed, wherein theindicator of power adjustment comprises at least one of lowering powerand lowering interference timeslots.

According to another exemplary embodiment there is provided aninterference coordination device in a wireless communication system,comprising: a determination unit configured to determine whetherinterference to a target small cell satisfies a predetermined condition;and a control unit configured, in a case that the interference to thetarget small cell satisfies the predetermined condition, to control thetarget small cell base station to adjust power at least based upon thenumber of users in a coverage area thereof, and/or to control the targetsmall cell base station to request other small cell base station orstations producing interference thereto to adjust power at least basedupon the number of users in a coverage area of the other small cell basestation or stations producing the interference to lower the interferenceto the target small cell.

According to the above device, the interference coordination device isarranged at a small cell base station side or a macro base station side.

According to another exemplary embodiment there is provided ameasurement device in a wireless communication system, comprising: ameasurement unit configured to obtain interference to each user in acoverage area of each small cell base station in the wirelesscommunication system and to send the interference to each user to aservice base station of the user, wherein the service base station ofthe user is provided with the interference coordination device above.

It should also be illustrated that a relational term such as left andright, a first or a second herein is only used to distinguish one entityor operation from another entity or operation, and does not necessarilyrequire or imply that there is an actual relationship or sequencebetween these entities or operations. Also, terms “comprise”, “include”or any other variants are intended to cover non-exclusive “include”, sothat a procedure, a method, an object or an equipment including a seriesof elements not only include the series of elements, but also includeother elements not explicitly listed, or also include elements inherentto the procedure, the method, the object or the equipment. Without morelimitation, an element defined in a sentence “include one . . . ” doesnot exclude the existence of another same element in the procedure, themethod, the object or the equipment including said element.

The invention claimed is:
 1. A system comprising: circuitry configuredto determine to modify transmission power of a first small cell basestation; determine an effect of modifying the transmission power of thefirst small cell base station on a user equipment that is served by thefirst small cell base station; and control modifying the transmissionpower of the first small cell base station based on the determination tomodify the transmission power and the determined effect of modifying thetransmission power on the user equipment that is served by the firstsmall cell base station; wherein the circuitry is further configured tocontrol the first small cell base station to reduce transmission powerwhen it is determined that an interference in the first small cell basestation or a second small cell base station located adjacent to thefirst small cell base station exceeds a predetermined threshold value.2. The system of claim 1, wherein the first small cell base station isprovided in a same area as a macro cell base station, the first smallcell base station having a smaller coverage area than the macro cellbase station.
 3. The system of claim 1, wherein the circuitry isconfigured to control increasing the transmission power when apredetermined condition is satisfied, the predetermined conditionincluding at least one of the interference in the first small cell basestation or the second small cell base station located adjacent to thefirst small cell base station reducing below the predetermined thresholdvalue; a number of user equipment requesting access to the first smallcell base station exceeds the predetermined threshold value; and storedscheduling information indicates that the transmission power of thefirst small cell base station should be increased at a predeterminedtime and/or date.
 4. The system of claim 1, wherein a coverage area ofthe first small cell base station includes a central region includinguser equipment having a first level of interference and an edge regionincluding user equipment having a second level of interference that isgreater than the first level of interference.
 5. The system of claim 4,wherein the circuitry is configured to determine the effect of modifyingthe transmission power of the first small cell base station based on anumber of user equipment in the central region and a number of userequipment in the edge region.
 6. The system of claim 5, wherein thecircuitry is configured to not reduce the transmission power of thefirst small cell base station when the number of user equipment in theedge region exceeds the predetermined threshold value.
 7. The system ofclaim 1, wherein the circuitry is configured to reduce the transmissionpower of the first small cell base station until it is determined thatuser equipment no longer capable of accessing the first small cell basestation are not able to be handed over to another cell base station. 8.The system of claim 4, wherein the circuitry is configured to determinewhether a number of user equipment in the central region of the coveragearea of the first small cell base station is less than the predeterminedthreshold value.
 9. The system of claim 8, wherein the circuitry isconfigured to reduce transmission power of the first small cell basestation to service only user equipment located in the central region ofthe cell base station when the number of user equipment in the centralregion of the coverage area of the first small cell base station isgreater than the predetermined threshold value.
 10. The system of claim8, wherein the circuitry is configured to reduce transmission power ofthe first small cell base station such that the first small cell basestation is not able to transmit a downlink signal to a user equipment,but is capable of communicating with another base station when thenumber of user equipment in the central region of the coverage area ofthe first small cell base station is less than the predeterminedthreshold value.
 11. The system of claim 4, wherein the circuitry isconfigured to determine a ratio of a number of user equipment in thecentral region and a number of user equipment in the edge region. 12.The system of claim 11, wherein the circuitry is configured to reducetransmission power of the first small cell base station to service onlyuser equipment located in the central region of the first small cellbase station when the ratio is greater than the predetermined thresholdvalue.
 13. The system of claim 1, wherein the circuitry is configured toidentify a first user equipment served by the first small cell basestation that is subject to a highest level of interference among aplurality of user equipment served by the first small cell base station.14. The system of claim 13, wherein the circuitry is configured todetermine whether the first user equipment is capable of being handedover to a macro cell base station serving the same area of the firstsmall cell base station or the second small cell base station adjacentto the first small cell base station.
 15. The system of claim 14,wherein the circuitry is configured to instruct the first user equipmentto handover to the macro cell base station or the second small cell basestation and control reduction of the transmission power of the firstsmall cell base station based on the handover of the first userequipment.
 16. The system of claim 1, wherein the circuitry isconfigured to: determine that reducing the transmission power of thefirst small cell base station would cause a user equipment that is notcapable of being handed over to another cell base station to no longerbe capable of accessing the first small cell base station or cause anumber of user equipment above a threshold value to no longer be capableof accessing the first small cell base station; and control reducingtransmission power of a second small cell base station causinginterference to the first small cell base station or control increasingtransmission power of the first small cell base station when it isdetermined that reducing the transmission power of the first small cellbase station would cause the user equipment that is not capable of beinghanded over to another cell base station to no longer be capable ofaccessing the first small cell base station or cause a number of userequipment above a threshold value to no longer be capable of accessingthe first small cell base station.
 17. A non-transitorycomputer-readable medium including computer-readable instructions, whichwhen executed by a system, cause the system to: determine to modifytransmission power of a first small cell base station; determine aneffect of modifying the transmission power of the first small cell basestation on a user equipment that is served by the first small cell basestation; and control modifying the transmission power of the first smallcell base station based on the determination to modify the transmissionpower and the determined effect of modifying the transmission power onthe user equipment that is served by the first small cell base station;wherein the system is further configured to control the first small cellbase station to reduce transmission power when it is determined that aninterference in the first small cell base station or a second small cellbase station located adjacent to the first small cell base stationexceeds a predetermined threshold value.
 18. A method performed by asystem, the method comprising: determining, by circuitry of the system,to modify transmission power of a first small cell base station;determining, by the circuitry of the system, an effect of modifying thetransmission power of the first small cell base station on a riserequipment that is served by the first small cell base station; andcontrolling, by the circuitry of the system, modifying the transmissionpower of the first small cell base station based on the determination tomodify the transmission power and the determined effect of modifying thetransmission power on the user equipment that is served by the firstsmall cell base station; wherein the first small cell base station isfurther controlled, by circuitry, to reduce transmission power when itis determined that an interference in the first small cell base stationor a second small cell base station located adjacent to the first smallcell base station exceeds a predetermined threshold value.